The following is information about a rust disease attacking Callery pears in Delaware.
CEDAR-QUINCE RUST
Samples of 'Bradford' Callery pear fruit and 'Redspire' have been diagnosed with cedar-quince rust. Since pear is in the same family as hawthorn and serviceberry--usual hosts of this rust, it stands to reason that pears could be infected as well. But, pear is a new host for this common disease. Infected fruit have the elongated white tube structures that protrude and turn orange with time. It is a superficial disease that only infects the fruit. So only the appearance of plants are affected not overall health. Since Bradford pears don't set lots of fruit anyway it may be hard to spot infected ones. Since there is concern over Bradford pears setting fruit and escaping into the landscape it will be interesting to learn if infected fruit can produce normal seed and germinate.
Information from Bob Mulrooney, Extension Plant Pathologist, UD
Showing posts with label pear. Show all posts
Showing posts with label pear. Show all posts
Monday, July 27, 2009
Thursday, June 11, 2009
Landscape and Nursery - Bacterial Shoot Blight
The following is information on bacterial shoot blight, a disease now active in the landscape.
Bacterial Shoot Blight or Syringae blight is caused by a bacterium Pseudomonas syringae and its many pathovars. It can cause leaf spots, blights and cankers on susceptible hosts. This disease has been very active in the landscape on many hosts especially lilac, cherries, rose, apple, pear, willow, and photinia. Sometimes the damage on cherries and lilac can resemble fire blight on apple. On green twigs, lesions can appear as black streaks. On lilac, green shoots die, turn black and shrivel. Leaf spots are irregularly shaped, brown and often with yellow halos. Once the dieback dries out, the damaged stems can be pruned out. There are no effective chemical controls in the landscape. Applications of copper containing fungicides and streptomycin could reduce epiphytic populations of the bacteria in production nurseries during wet seasons, but for the homeowner it is probably best to wait it out and prune.
Symptoms of bacterial blight (Pseudomonas syringae) on leaves of a lilac. Photo by William Jacobi, Colorado State University, Bugwood.org.
Signs and symptoms of bacterial blight (Pseudomonas syringae) on a lilac. Photo by William Jacobi, Colorado State University, Bugwood.org.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.
Bacterial Shoot Blight or Syringae blight is caused by a bacterium Pseudomonas syringae and its many pathovars. It can cause leaf spots, blights and cankers on susceptible hosts. This disease has been very active in the landscape on many hosts especially lilac, cherries, rose, apple, pear, willow, and photinia. Sometimes the damage on cherries and lilac can resemble fire blight on apple. On green twigs, lesions can appear as black streaks. On lilac, green shoots die, turn black and shrivel. Leaf spots are irregularly shaped, brown and often with yellow halos. Once the dieback dries out, the damaged stems can be pruned out. There are no effective chemical controls in the landscape. Applications of copper containing fungicides and streptomycin could reduce epiphytic populations of the bacteria in production nurseries during wet seasons, but for the homeowner it is probably best to wait it out and prune.
Information from Bob Mulrooney, Extension Plant Pathologist, UD.
Monday, June 8, 2009
Landscape - Fire Blight
Fire blight is being seen in ornamental pears and other landscape plants at this time in Delaware. The following is a good article on the subject from Rutgers University.
Fire blight is a relatively common disease caused by a bacterium (Erwinia amylovora). Fire blight can occur on many rosaceous plants, including crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear. Although we see this disease most often in pyracantha, some ornamental pears in central New Jersey have been recently diagnosed with the disease. Development of fireblight usually begins in the spring as bacterial cells ooze in a yellow-amber liquid from existing cankers on infected plants. These cells are spread to susceptible flowers, leaves, fruit, and stems by insects, wind, splashing rain, or pruning equipment. Insects are especially attracted to this sweet, sticky, bacterial ooze; bees and other pollinating insects commonly pick up bacteria while visiting the cankers and subsequently deposit the cells on developing flowers. Erwinia bacteria penetrate tissue through wounds and natural openings such as stomates and nectaries. Twigs and branches infected with the pathogen die rapidly and appear scorched, hence the name “fireblight.” Tender shoots tend to droop and bend as they die, developing a symptom commonly associated with the disease called a shepherd’s crook. As the disease advances, cankers form at the base of infected branches, and highly susceptible plants may die. Conditions optimal for fireblight development are extended periods of warm (greater than 65 to 75 F), wet weather during spring.
To manage the disease, improve plant vigor, but avoid heavy spring fertilization that would promote succulent growth. In late summer (after bacterial oozing no longer occurs), prune all diseased wood at least 6 to 8 inches below the infection, surface sterilizing tools between cuts. Remove water sprouts, and dispose of any infected plant material which may harbor the pathogen. The following bactericides have labels for fire blight (check for host, timing, and rates): copper (Badge, hydroxide, metallic, salts, sulfate), fosetyl- Al (pre-bloom and repeat every 7 days until bloom), Junction (5-day intervals during bloom), OR phosphite (7-day intervals through bloom). Finally, consider repeatedly diseased, highly susceptible plants with material that is more resistant to this disease. Highly susceptible callery pears include Aristocrat, Autumn Blaze, Capital, Fauriei, and Redspire; moderately susceptible cultivars include Cleveland Select, Earlyred, and Whitehouse. Although Bradford is reported to be moderately resistant in certain locations, it will develop fireblight under conditions optimal for disease development, as we noticed last year.
Fire blight on ornamental pear. Photo from the Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org.
Information from Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University.
Fire blight is a relatively common disease caused by a bacterium (Erwinia amylovora). Fire blight can occur on many rosaceous plants, including crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear. Although we see this disease most often in pyracantha, some ornamental pears in central New Jersey have been recently diagnosed with the disease. Development of fireblight usually begins in the spring as bacterial cells ooze in a yellow-amber liquid from existing cankers on infected plants. These cells are spread to susceptible flowers, leaves, fruit, and stems by insects, wind, splashing rain, or pruning equipment. Insects are especially attracted to this sweet, sticky, bacterial ooze; bees and other pollinating insects commonly pick up bacteria while visiting the cankers and subsequently deposit the cells on developing flowers. Erwinia bacteria penetrate tissue through wounds and natural openings such as stomates and nectaries. Twigs and branches infected with the pathogen die rapidly and appear scorched, hence the name “fireblight.” Tender shoots tend to droop and bend as they die, developing a symptom commonly associated with the disease called a shepherd’s crook. As the disease advances, cankers form at the base of infected branches, and highly susceptible plants may die. Conditions optimal for fireblight development are extended periods of warm (greater than 65 to 75 F), wet weather during spring.
To manage the disease, improve plant vigor, but avoid heavy spring fertilization that would promote succulent growth. In late summer (after bacterial oozing no longer occurs), prune all diseased wood at least 6 to 8 inches below the infection, surface sterilizing tools between cuts. Remove water sprouts, and dispose of any infected plant material which may harbor the pathogen. The following bactericides have labels for fire blight (check for host, timing, and rates): copper (Badge, hydroxide, metallic, salts, sulfate), fosetyl- Al (pre-bloom and repeat every 7 days until bloom), Junction (5-day intervals during bloom), OR phosphite (7-day intervals through bloom). Finally, consider repeatedly diseased, highly susceptible plants with material that is more resistant to this disease. Highly susceptible callery pears include Aristocrat, Autumn Blaze, Capital, Fauriei, and Redspire; moderately susceptible cultivars include Cleveland Select, Earlyred, and Whitehouse. Although Bradford is reported to be moderately resistant in certain locations, it will develop fireblight under conditions optimal for disease development, as we noticed last year.
Information from Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University.
Monday, April 14, 2008
Landscape and Nursery - Fireblight
Fireblight can be a problem on certain ornamental plants in the rose family. Flowering is a critical time for infection. The following is an article on the subject.
Fire blight, caused by the bacterium Erwinia amylovora, is a serious disease of many ornamental species in the Rosaceae family. Certain varieties of apple, flowering crabapple, pear, pyracantha, and quince are highly susceptible. Other plants, such as hawthorn, Japanese quince, mountain ash, rose, cotoneaster, spirea, loquat, and amelanchier, may occasionally also be damaged.
Symptoms
Blossoms, young fruits, small twigs, leaves and water sprouts are susceptible to infection. Blossoms and leaves wilt suddenly, turn dark brown to black, shrivel, and die, but usually remain attached to the plant. Leaves are often infected through the petiole and, on some plants, blackening of the petiole and adjacent tissue can be seen before the whole leaf dies. Infected fruit becomes leathery in appearance. Cankers on limbs are characteristically shrunken and dark brown to purplish in color. Dark streaking in the wood often extends several inches beyond any surface discoloration. Secondary infections start in the small twigs, progress down the stem, and may eventually involve whole branches. Severely blighted plants appear to have been scorched by fire. A characteristic symptom of fire blight is the bending of the blighted terminal, which resembles a shepherd's crook.
Disease Cycle
The bacteria overwinter in cankers and begin multiplying in the spring. Milky white to cream-colored bacterial slime, containing millions of bacteria, may ooze from the cankers in the spring. The bacteria grow most rapidly at 24°-29°C (75°-84°F). They are disseminated by wind-blown rain, certain insects, and pruning tools. Primary infections usually occur through the flowers at bloom, but bacteria quickly spread to twigs and leaves. The bacteria often invade wounds, and infection can be especially severe after hail storms. By mid to late summer bacterial multiplication slows as cankers form. As the bark tissues die, so do the bacteria, but bacteria may remain active at canker margins until the fall.
Control
During the late summer when bacterial growth slows, all infected twigs and branches should be pruned out and burned or buried. Because the bacteria are usually found somewhat in advance of the obviously diseased tissue, the cut should be made through healthy wood 6 to 8 inches below the point of visible infection. Cankered areas on large branches and trunks should be pruned out during the dormant season. Pruning tools should be sterilized frequently with rubbing alcohol or dilute household bleach (1 part bleach to 9 parts water) during this operation to prevent introducing the bacteria to new wood.
Fire blight is worse on succulent tissues. Avoid excessive use of nitrogenous fertilizers and excessive pruning, both of which promote succulent growth. Remove water sprouts that form on susceptible tree species as they appear. Water sprouts are very susceptible to infection and can provide direct access of the bacteria to the trunk.
Reprinted in part from "Fire Blight of Ornamentals" by Mary Ann Hansen, Extension Plant Pathologist, Department of Plant Pathology, Physiology and Weed Science, Virginia Tech http://www.ext.vt.edu/pubs/plantdiseasefs/450-610/450-610.html
Fire blight, caused by the bacterium Erwinia amylovora, is a serious disease of many ornamental species in the Rosaceae family. Certain varieties of apple, flowering crabapple, pear, pyracantha, and quince are highly susceptible. Other plants, such as hawthorn, Japanese quince, mountain ash, rose, cotoneaster, spirea, loquat, and amelanchier, may occasionally also be damaged.
Symptoms
Blossoms, young fruits, small twigs, leaves and water sprouts are susceptible to infection. Blossoms and leaves wilt suddenly, turn dark brown to black, shrivel, and die, but usually remain attached to the plant. Leaves are often infected through the petiole and, on some plants, blackening of the petiole and adjacent tissue can be seen before the whole leaf dies. Infected fruit becomes leathery in appearance. Cankers on limbs are characteristically shrunken and dark brown to purplish in color. Dark streaking in the wood often extends several inches beyond any surface discoloration. Secondary infections start in the small twigs, progress down the stem, and may eventually involve whole branches. Severely blighted plants appear to have been scorched by fire. A characteristic symptom of fire blight is the bending of the blighted terminal, which resembles a shepherd's crook.
Disease Cycle
The bacteria overwinter in cankers and begin multiplying in the spring. Milky white to cream-colored bacterial slime, containing millions of bacteria, may ooze from the cankers in the spring. The bacteria grow most rapidly at 24°-29°C (75°-84°F). They are disseminated by wind-blown rain, certain insects, and pruning tools. Primary infections usually occur through the flowers at bloom, but bacteria quickly spread to twigs and leaves. The bacteria often invade wounds, and infection can be especially severe after hail storms. By mid to late summer bacterial multiplication slows as cankers form. As the bark tissues die, so do the bacteria, but bacteria may remain active at canker margins until the fall.
Control
During the late summer when bacterial growth slows, all infected twigs and branches should be pruned out and burned or buried. Because the bacteria are usually found somewhat in advance of the obviously diseased tissue, the cut should be made through healthy wood 6 to 8 inches below the point of visible infection. Cankered areas on large branches and trunks should be pruned out during the dormant season. Pruning tools should be sterilized frequently with rubbing alcohol or dilute household bleach (1 part bleach to 9 parts water) during this operation to prevent introducing the bacteria to new wood.
Fire blight is worse on succulent tissues. Avoid excessive use of nitrogenous fertilizers and excessive pruning, both of which promote succulent growth. Remove water sprouts that form on susceptible tree species as they appear. Water sprouts are very susceptible to infection and can provide direct access of the bacteria to the trunk.
Reprinted in part from "Fire Blight of Ornamentals" by Mary Ann Hansen, Extension Plant Pathologist, Department of Plant Pathology, Physiology and Weed Science, Virginia Tech http://www.ext.vt.edu/pubs/plantdiseasefs/450-610/450-610.html
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